Nicotine. Molecular graphic of nicotine, an addictive alkaloid drug found in tobacco. Nicotine (formula: C10.H14.N2) is an oily, colourless liquid. The atoms, represented as sticks, are colour-coded: carbon (grey), nitrogen (blue) and hydrogen (white). A slice through the molecule (yellow) shows the distribution of charge (electrostatic potential) in this plane. Nicotine is the active component of tobacco. In small doses it stimulates the autonomic nervous system, but tolerance builds up fast, leading to addiction. As well as the toxic effects of nicotine, smoking tobacco can lead to serious lung problems, including lung cancer.